Consider "HEAD" releases dev snapshots.

when i moved all the CVS-specific code to cvs_deploy.module (http://drupal.org/node/150316), we lost the ability to ignore HEAD checkouts as dev releases. i see 3 possible solutions:

1) add a CVS-specific special-case directly to update_status.module in update_status_get_projects(), so that if the final version string is "HEAD" we set $type = 'dev'. this is simple, but it re-introduces CVS-specific logic into update_status.module, which i'd really like to avoid.

2) introduce another alter hook, to give other modules a chance to modify the update_status $type variable for each module (to indicate it's really a dev release, etc, etc). i'm proposing "hook_status_type_alter()", and that's what's in the attached patch (which adds the hook invokation to update_status, and the proposed implementation of the hook to cvs_deploy).

3) make it so the existing hook_version_alter() gets to alter both the version string and the $type. i don't like this approach at all, but i figured i'd mention it as a possible alternative to a whole new hook.

unlike a bunch of my other recent changes which i just committed directly without issues, patches, and discussion, this one seems like it requires more consideration, so please comment thoughtfully here.

thanks,
-derek